I. Field of the Invention
This invention relates generally to vehicle ladder racks for use in loading and unloading heavy ladders onto and from the roof of a motor vehicle, and more particularly to such ladder racks especially adapted for use on so-called xe2x80x9chi bay vansxe2x80x9d where the roof of the van is sufficiently high to pen-nit an adult to stand upright within the body of the van.
II. Discussion of the Prior Art
In my earlier U.S. Pat. 5,297,912 (the ""912 patent), the contents of which are hereby incorporated by reference as if set forth in full herein, I describe a motor vehicle ladder rack for use on conventional sports utility vehicles (SWV""s) and vans of the type commonly sold in the United States. Such vehicles may typically have a roof height of only about 6.5 feet (1.98 meters). Here, my earlier disclosed embodiment of the ""912 patent works very well in that an adult can readily reach and manipulate the handle 58 of the crank used to rotate the connector rod 50 throughout its entire range of motion. In the case of hi bay vans, however, where the roof height is typically about 9 feet (2.75 m), not only must the ladder rack allow for a greater drop-down distance to facilitate ease of removal and loading of ladders from a position alongside of the vehicle, but also, the actuating lever used in raising and lowering the ladders must remain reachable over its entire range of travel. In the ladder rack product built in accordance with the disclosure in the ""912 patent, the crank 56 used to rotate the connector rod 52 for moving a ladder load to and from its stowed position atop the vehicle""s roof 12 had to swing through an arc of about 180xc2x0. While this did not present a problem for ladder racks on conventional vans, with hi bay vans, the crank on my prior art type ladder rack would be out of reach for most persons at the start and end of the 180xc2x0 swing where the crank handle 58 is generally horizontal.
A need therefore exists for an improved ladder rack actuating mechanism that is usable with ladder rack assemblies mounted on hi bay vans and which allow a person to readily move ladders from a stowed disposition on the vehicle""s roof to a deployed location alongside the vehicle and back again in an economically convenient and safe manner.
In accordance with the present invention, I have devised an actuating mechanism for rotating the connector rod of my ladder rack which can be readily reached and held throughout the entire range of movement of the ladder load between its stowed and deployed states, even when mounted on a hi bay style vehicle.
The present invention provides an improved apparatus for facilitating the loading and unloading of a ladder from the roof of a motor vehicle and comprises first and second four-bar linkage assemblies where each includes a stationary bar member adapted for attachment to the roof of a motor vehicle in parallel, spaced-apart relation so as to extend transversely to the longitudinal axis of the motor vehicle and a moveable bar member comprising a ladder rest pivotally coupled to the stationary bar member by a pair of rigid links of unequal length. The pair of rigid links are sized and positioned such that rotation of one of the pair of rigid links on each of the first and second 4-bar linkage assemblies results in the moveable bar member that comprises the ladder rest to move between a first disposition which is generally parallel to the roof of the vehicle and a second disposition aligned with and spaced from one side of the vehicle. A connector rod extends longitudinally between the first and second 4-bar linkage assemblies and is journaled for rotation in the stationary bar members of each of the 4-bar linkage assemblies. The connector rod is operatively coupled to the one of the pair of rigid links. The connector rod is adapted to be driven by a mechanism that includes a lever that is pivotable about a fixed fulcrum to define lever arms of lengths L1 and L2 where L1 is much greater than L2. A rotatable coupler is journaled for rotation about the connector rod and has a radially extending arm of length L3 pivotally joined by a link member to an end portion of the lever arm L2. The ratio of L3 to L2 increases the angular travel of the rotatable coupler to be about double that of the driving lever. The rotatable coupler cooperates with the connector rod to apply a torque to the connector rod only when a force is applied to the lever arm, L1, to pivot the lever through a predetermined angle which is less than about 45xc2x0 from the vertical. In that the ladder load may be raised and lowered from the roof of the vehicle by manipulating the lever through an angle of about 90xc2x0 centered about the vertical, it always remains well within reach of an adult worker.